Process of treating cashew nut shell liquid



Patentecl Nov. 18, 1947 PROCESS OF TREATING CASHEW NUT SHELL LIQUIDRoland E. Kremers, Summit, N. J., assignor to General Foods Corporation,Hoboken, N. J., a

corporation of Delaware No Drawing. Application April 29, 1944, SerialNo. 533,409

11 Claims.

This invention relates to a process of separating the acid constituentfrom cashew nut shell liquid or hydrogenated cashew nut shell liquid.This application is a continuation-in-part of my copending applicationSerial Number 441,758, filed May 4, 1942 (now Patent No. 2,380,319)

The principal object of the present invention is to provide a process bywhich the acid constituent may be easily and economically separated fromcashew nut shell liquid or hydrogenated cashew nut shell liquid, whichprocess possesses none of the disadvantages of the prior processes andprovides a much sharper separation of the acid from the toxic phenolicconstituents of the liquid than has heretofore been obtainable.

Other objects will be apparent from a consideration of the specificationand the claims.

While cashew nut shell liquids of commerce have been used or suggestedfor use for various purposes, as for example in the manufacture ofprinting inks, varnishes, synthetic resins, molding compositions, andthe like, anacardic acid and its derivatives have recently beensuggested for the same purposes and also as ingredients of oil sprays,oil dips, insecticides, dyestuff and pharmaceutical intermediates, etc.Tetrahydroanacardic acid has also been suggested as an ingreclient ofinsecticides, dyestufi and pharmaceutical intermediates and the like.

Heretofore, as far as I am aware, anacardic acid has been produced fromcashew nut shell liquid by either one of two methods. In one method,cashew nut shell liquid is treated with a basic lead compound whereuponthe anacardic acid precipitates as crude lead anacardate. Thisprecipitate is separated by any suitable means such as filtering,centrifuging, etc, and, following separation, it is converted into crudeanacardic acid by treating with acid. In the other method (see Balvalli,U. S. Patent No. 2,230,995), cashew nut shell liquid is treated with abasic sodium, or other alkali, compound whereupon a gel composed ofsodium anacardate and the nonacidic portion of the liquid is formed. Thegel is leached with a suitable solvent to dissolve and remove thegreater proportion of the non-acidic material from the sodiumanacardate, and, following leaching, the crude sodium anacardate isconverted into crude anacardic acid by treatment with acid.

These procedures for the production of anacardic acid, however, leavemuch to be desired. The anacardol and other phenolic materials of thenon-acidic portion of the liquid react to a considerable extent withbasic lead compounds and the insoluble compounds formed precipitateconjointly with the anacardate. Consequently, when the anacardic acid isregenerated it is contaminated with considerable phenolic impurities. Infact, some of the phenolic constituents react so readily with the basiclead compounds that reprecipitation of the anacardic acid is onlymoderately effective for their removal. Reaction of cashew nut shellliquid with a basic sodium, or other alkali, compound is equallyunselective and yields a gel, rather-than a precipitate. Thisnecessitates a tedious liquid-liquid extraction of the aqueous phasewith a suitable immiscible solvent such as hexane, benzene, petroleumether, and the like. By such a process, only low yields of reasonablypure anacardic acid are obtainable and if high yields of anacardic acidare desired, the purity of the product is necessarily low. Thus, inorder to prepare reasonably pure anacardic acid through the formation ofeither the basic lead or sodium anacardates, the procedures ofpurification are so involved as to render such preparation practicalonly in the laboratory.

The production of tetrahydroanacardic acid is similarly complicated,whether the procedure used involves hydrogenation of cashew nut shellliquid followed by treatment with lead or sodium compounds, or treatmentof the cashew nut shell liquid with lead or sodium compounds followed byhydrogenation of the crude anacardic acid. Purification is somewhatsimpler in the case of the tetrahydroanacardic acid, however, since itcrystallizes more readily due to its higher melting point, as comparedwith anacardic acid. Nevertheless, the proportion of non-acidicimpurities which contaminates the tetrahydroanacardic acid obtained bytreatment with lead or sodium compounds is comparable to thatencountered in the production of anacardic acid by the same methods.

Cashew nut shell liquid, as it exists in the nut shells, contains alarge proportion of anacardic acid and a small proportion of non-acidicmaterial known generally as the cardolic fraction. The non-acidicportion of the liquid includes various phenols, one of which isanacardol. While anacardol is probably present to some extent in theliquid naturally occurring in the nut shells, it owes its presence inthe commercial liquids largely to its formation from anacardic acid.Thus in the older methods of extraction which rely on heat to destroythe cellular structure of the shells, a large proportion of theanacardic acid, originally contained in the shells, is converted to ana-3 cardol. Gn the other hand, the liquids obtained by modern methodsdepending on pressure, or cold-pressing of the shells, contain largeamounts of anacardic acid in proportion to the amount of anacardol, and,therefore, whereas the anacardic acid content of heat-extracted liquidsis not generally greater than 16%, the liquids obtained by pressureextraction are known to contain up to 2 8% or anacardic acid.

The starting material in the process of the present invention may becashew nut shell liquid obtained by either of the above-describedmethods of extraction or, in fact, by any other method, such as solventextraction of the shells, provided that an appreciable amount ofanacardic acid is contained therein, or it may be any hydrogenatedcashew nut shell liquid containing an appreciable amount oftetrahydroanacardic acid, i. e., anacardic acid having its aliphaticside chain hydrogenated. Hence, the invention can be applied to cashewnut shell liquids or hydrogenated cashew nut shell liquids, whether highor low in acid content, for the production of anacardic acid ortetrahydroanacardic acid, although the process is particularlyapplicable for the treatment of liquids having a relatively high contentof anacardic acid or tetrahydroanacardic acid, that is an acid contentof at least 40%. It is to be further understood that the invention isapplicable for the treatment of any fraction of the cashew liquidcontaining anacardic acid, or of any hydrogenated fraction of the liquidor fraction of hydrogenated cashew liquid containing tetrahydroanacardicacid. Furthermore, the rocess may be employed in the-separation of theacid constituent from cashew nut shell liquid or hydrogenated cashew nutshell liquid or a fraction thereof which has been partiallycarboxylated, for example, by a method analogous to the Kolbe methodemployed in the production of salicylic acid from phenol. All of theaforementioned various liquids are included in the phrase, a liquidselected from the group consistin of cashew nut shell liquid andhydrogenated cashew nut shell liquid.

For convenience, the invention is hereinafter defined, and itsprocedures described, largely in connection with the production ofanacardic acid from cashew nut shell liquid. It is understood, however,that the procedures described are equally applicable to the productionof tetrahydro-anacardie acid from hydrogenated cashew nut shell liquid,and to the separation of the acid constituent from a carboxylated cashewnut shell liquid.

The invention comprises reacting the acid in cashew nut shell liquid orhydrogenated cashew nut shell liquid with alkaline earth metal ions toform the alkaline earth metal salt, separating the salt from toxicphenolic constituents associated therewith, regenerating the organicacid from the separated salt by an acid capable of displacing theorganic acid from the salt, and separating the organic acid liberatedfrom the salt from the reaction mixture. As I have found, the phenolicmaterials of the non-acidic portion of the liquid react to only a slightextent with alkaline earth metal ions and consequently a much sharperseparation of acid contained in the liquid treated from the phenolicmaterials is obtained than has been possible by previously knownprocesses. An acid of a high degree of purity may, therefore, beobtained by relatively simple procedures of purification.

A practical process for the production of anacardic acid ortetrahydroanacardic acid of a high degree of purity is of particularutility. It has long been apparent that the dermatitis produced inindividuals by cashew nut shell liquid has been the primary obstacle tothe wider use of the liquid. In studying a related problem, Majima (Ber.42, 1418 ($09)) showed that urushiol, a homologue of catechol, is thetoxic constituent of Japanese lac. Since the time of ,Majimaspublication, it has been believed that the toxicity of cashew nut shellliquid was likewise due to the presence of urushiol, or some homologousor otherwise similar compound. In accordance with this belief, attemptsto detoxify cashewnut shell liquid have been directed to the destructionor inactivation of the urushiol, as, for example, by reacting withproteins or analogous materials (see Cayo, U. S. Nos. 2,183,957 and2,188,958), but no certain method has been devised for providingnon-toxic cashew materials which are safe to handle. I have discovered,however, that anacardol is highly toxic and, in view or" the recognizedtoxicity of the urushiol type compounds and the discovered toxicity ofanacardol, it is quite possible that all of the phenolic constituents ofcashew nut shell liquid are toxic. I have also found that, whileanacardol is toxic, anacardic acid is non-toxic. In the light of thesediscoveries, it will be apparent that, by producing anacardic acid ortetrahydroanacardic acid free from phenolic impurities, I have providedcashew materials that are non-toxic and safe to handle.

The alkaline earth metal ions which are employed in the process of theinvention are those of calcium, barium, and strontium. It is to beunderstood that magnesium ions are not included within the term alkalineearth metal ions, although as hereinafter pointed out a relatively smallamount of magnesium ions may be present with the calcium or otheralkaline earth ions. In the practice of the invention, the basiccompounds, such as the oxide or hydroxide, of the alkaline earth metalscan be employed. The water-soluble neutral salts of the alkaline earthmetals, such as the chlorides, nitrates, and the like, can also beemployed, but since these do not react directly with anacardic acid, thecashew liquid in this case is first treated with a basic compound, as,for example, an aqueous solution of sodium or potassium hydroxide, toform a water-soluble anacardate which reacts readily with the neutralsalts to precipitate the alkaline earth metal anacardate. If desired,the cashew nut shell liquid can be treated first with the neutral saltand then with the basic compound, or the neutral salt and the basiccompound can be mixed together and the cashew nut shell liquid treateddirectly with this mixture. The claims which state that alkaline earthmetal ions are reacted with ions of the acid of the liquid to form thealkaline earth metal salt of the acid includes both the direct reactionof the oxide or hydroxide with the acid and the reaction of a solublesalt of the acid with an alkaline earth metal salt.

Of the alkaline earth metal compounds available for use, the oxides orhydroxides are generally preferred, and due to the availability ofslaked and unslaked lime, these compounds may advantageously beemployed. The alkaline earth metal oxides and hydroxides are includedherein in the term basic alkaline earth metal compound. It has beenfound that the lime used represented by the following structuralformulas:

. OH OH we OH 0 0 o H K/CuHw k/Cw ai Anacardic acid Tetrahydroanacardicacid Both acids are capable of forming a neutral salt and a basic saltwith alkaline earth metal ions, as shown in the following formulas,using the calcium salts of anacardic acid as illustrative:

OH no qCOOOaOOC K/CHHZT CitHzi Neutral calcium anacardate Basic calciumanacardatc The neutral salt is not completely insoluble in such solventsas acetone, ethanol, and isopropanol, whereas the basic salt is quiteinsoluble in such solvents. Hence, it is desirable to form the basicsalt of the anacardio acid as such solvents are generally employed toeffect the solution of the unreacted material. As will be observed fromthe above formulas, the molratio of anacardic acid to alkaline earthmetal ion is 2 to 1 in the case of the neutral salt and 1 to 1 in thecase of the basic salt. Consequently, in order to form the basic salt,at least 1 mol of alkaline earth metal compound is reacted with each molof anacardic acid contained in thecashew nut shell liquid. However, inorder to insure complete conversion of the anacardic acid to the basicsalt, it is desirable to use the alkaline earth metal compound in excessof 1 mol. For example, in the case of cashew nut shell liquid containing65% of anacardic acid by weight, satisfactory results will be obtainedby employing slaked lime in the range from about 14% to 25% based on theweight of the liquid, the use of approximately 17% of unslaked limebeing usually preferred. It will be understood that equivalent amountsof other materials furnishing alkaline earth metal ions may be used andthat the amount employed will be dependent upon the anacardic acidcontent of the liquid. In fact, as stated, the amount of alkaline earthcompound may be varied widely; for example, when the efiiciency of theprocess is not important, the amount of alkaline earth ions availablefor reaction may be insuflicient to form the basic salt and may only besufficient to convert a portion of the acid into the neutral salt. Onthe other hand, an excess over that required to convert all of the acidinto the basic salt is not deleterious except that its use represents aloss of material.

V The cashew nut shell liquid can be treated with the alkaline earthmetal compound in any desired manner. When an alkaline earth metal oxideor hydroxide is used, the treatment can be effected without appreciablydiluting either reactant (by solution or dispersion in suitable media)to obtain the hardened plastic product of my copending applicationSerial No. 441,758, filed May 4, 1942. For example, the liquid per se oremulsified with a small amount of water can be treated with the alkalineearth metal oxide or hydroxide in the dry state to obtain the abovementioned hardened plastic product. As stated in the copendingapplication, the hardened plastic product will be obtained when theamount of alkaline earth metal oxide or hydroxide is employed in anamount in excess of that theoretically required to form a neutralalkaline earth metal salt of the anacardic acid content of the cashewnut shell liquid. It is preferable, however, to effect the treatment ofthe cashew nut shell liquid so that appreciable dilution of either, orboth, of the reactants is provided in order to obtain a finely dividedprecipitate of alkaline earth metal anacardate. Suitable media for thesolution or dispersion of the cashew nut shell liquid are acetone,isopropyl alcohol, aqueous sodium hydroxide, and the like, The cashewnut shell liquid thus dissolved or dispersed can be treated with thealkaline earth metal compound dissolved or dispersed in suitable mediasuch as water, isopropyl alcohol, or the like. In case the alkalineearth metal ions are to be provided by an alkaline earth metal salt, thecashew nut shell liquid may be mixed with a solution of a basiccompound, such as sodium or potassium hydroxide, and advantageously arelatively large volume of water is used. After the formation of thesoluble salt of anacardic acid, the alkaline earth salt is added, eitheras a solid or in solution, preferably the latter. The mixture isagitated and the alkaline earth metal anacardate forms as a precipitate.As stated above, the basic compound and the alkaline earth metal saltmay be dissolved in water and the solution added to the cashew nut shellliquid, or the solution of the alkaline earth metal salt may first beadded to the cashew nut shell liquid followed by the addition of thesolution of the basic compound.

Separation of the alkaline earth metal anaoardate formed by the reactioncan be accomplished by any suitable means. Where the aforementionedhardened plastic product is obtained, all of the non-acidic portion ofthe cashew nut shell liquid is contained therein and subdivision of theplastic product, followed by leaching with a suitable solvent for thenon-acidic portion of the liquid, as, for example, acetone, isopropylalcohol or aqueous sodium hydroxide, will eifeot separation of theanaoardate. The leaching can be efiected by any technique which providesfor contact between the solvent and the alkaline earth metal anacardate,withdrawal of the spent solvent, and replenishment with fresh solvent.Obviously, the leaching can be continued until the anacardate issubstantially free of surfaceheld impurities. Where the finely dividedprecipitate of alkaline earth metal anacardate is obtained, theseparation is readily efiected by filtration, decantation, orcentrifugation, and the anacardate is easily washed free fromsurfaceheld impurities with a suitable solvent. Whether the hardenedplastic form or the finely divided precipitate of the alkaline earthmetal anacardate is obtained, impurities will be occluded in the ascitric, tartaric, oxalic, etc.

tetrachloride, water-miscible solvent such as isopropyl alcohol,acetone, and the like.

undoubtedly combined with the alkaline earth subdivided plastic product,the anacardate is sufficiently hard to permit grinding to a more finelydivided state thereby exposing an additional amount of impurities, whichcan be removed by further leaching.

Regeneration of anacardic acid from the separated alkaline earth metalanacardate can be accomplished by treating the anacardate with any acidwhich is capable of displacing the anacardic acid from the salt, namely,one Which is stronger than anacardic acid (as measured by itsdissociation constant) or one which forms a salt with the alkaline earthmetal more insoluble than the alkaline earth metal anacardate (asmeasured by its solubility product). Suitable acids are mineral acidssuch as sulphuric, phosphoric, hydrochloric, etc., and organic acidssuch For manipulative reasons, the use of an acid which forms aninsoluble alkaline earth metal compound is preferred.

The amount of acid employed is advantageously sufficient to liberate allof the anacardic acid such as sulphuric, it is possible to employ themin any concentration desired. In case sulphuric acid is employed, theconcentration of the acid and the conditions of the treatment areselected so that appreciable polymerization will be avoided.

With aqueous media at room temperature, the regeneration reactionproceeds rapidly at the surface of the metallic anacardate, but theregenerated anacardic acid tends to form a coating over themetallicanacardate which prevents further progress of the reaction. This can beovercome by raising the temperature of the mixture, for example, toabout 50 C, to 70 C., and agitating vigorously to break the anacardicacid film, or by adding to the mixture a solvent for anacardic acid.This solvent may be a Water-immiscible solvent such as hexane, benzene,carbon chloroform, and the like, or a The first procedure, namely, theone employing vigorous agitation at slightly elevated temperatures,exposes the unreacted anacardate by emulsifying the regeneratedanacardic acid, whereas the second prohigher temperatures can beemployed for the purpose of increasing the rate of reaction.

Regardless of which of the procedures is used, however,

.the temperature employed should be below about 100 .C. in order toavoiddecarboxylation of the regenerated anacardic acid.

8 :Following regeneration, the anacardic acid can 'berecovered from thereaction mixture by relatively simple procedures, which will varydependingon whether-water and/or a solvent for anacardic acid ha's'beenemployed and whether the solvent is water-miscible or water-immiscible.

Where a solvent has not been employed, the regenerated anacardic acidseparates from the reaction mixture as a supernatant oil, which can beremoved by simple decantation. If the regeneration has been carried outin the presence of a water-immiscible solvent, the solvent phase can beseparated from the reaction mixture, as by decantation, and the solventevaporated for the recovery of the dissolved anacardic acid. Where awater-miscible solvent has been employed, the reaction mixture can befiltered to remove the solid residue, the filtrate evaporated, and theresidual anacardic acid recovered, or, preferably, the reaction mixturecan be extracted with a water-immiscible solvent for anacardic acid andthe anacardic acid thereafter recovered by evaporation of the solvent.

Using the procedures of my invention, I can obtain crude anacardic acidof -93% acid content upon regeneration of the alkaline earth metalanacardate, and upon further purification, as by treatment withcharcoal, recrystallization, or other known procedures, the acid contentcan be increased to 96-99%.

While the alkaline earth metal anacardates directly produced from cashewnut shell liquid after removal of the surface-held impurities arecontaminated to some extent by toxic non-acidic impurities, theseimpurities are confined to the interior of the solid particles.Absorption of the solid anacardates through the pores of the skin isnegligible, and hence the toxic contaminants are rendered inelrective.This is similarly true of the non-toxic solidified plastic productdescribed in my aforementioned copending application, Serial No.441,758. On the other hand, regeneration of the liquid anacardic acidfrom the anacardate liberates the toxic non-acidic impurities andrenders the crude anacardic acid somewhat toxic. The proportion of thetoxic contaminants, however, is small, and, as above stated, is easilremoved from-the anacardic acid by simple means of purification. Thus,the contaminants can be removed by treatment of a dilute solution of thecrude acid, for example a hexane solution, with charcoal; bycrystallization of the acid from such solvents as hexane, petroleumether, and the like, at temperatures of -20 C. to .l0 C.; or by theconversion of the anacardic acid into an alkali metalsaltand theliquid-liquid extraction of the aqueous solution thereof with a suitablesolvent suchas hexane, benzene, and the like, and the regeneration ofthe anacardic acid by treatment .with acid. Also, the toxic substancescan be removed from the crude anacardic acid by storage in kerosene,whereupon the toxic substances gradually precipitate as a dark-coloredgum, which can be readily separated bydecantation. In the caseiof,tetrahydroanacardic acid, prepared from hydrogenated cashew nut shellliquid, or by hydrogenation of thecrude regenerated anacardic acid,anadditional operative method of purification comprises the formation ofan alkali metal salt, such as that of sodium or potassium, andcrystallization of-the salt from water, followed by re eneration withmineralacid.

The :following specific examples will serve to illustrate and explainthe present invention.

EXAMPLE 1 Preparation of calcium anacardate 500 grams of cashew nutshell liquid, containing 63.5% of anacardic acid, which had beencentrifuged to remove solid impurities, were dissolved in 2 litres ofisopropyl alcohol. The solution was clarified by filtration withfilter-eel, which was added to the solution and also made up into a maton a Buchner funnel.

100 grams of slaked lime were weighed out and triturated to a thin pastewith a sufiicient quantity of water added in small portions.

The lime paste was transferred to a five-litre round bottom flask fittedwith a mechanical stirrer, and was suspended by agitation in 1 litre ofisopropyl alcohol. To this suspension, the filtered solution of cashewnut shell liquid was added in a small stream from a separatory funnel.The mixture was then stirred continuously until the reaction between thelime and the cashew liquid appeared to be complete. This was indi catedby reduction in the color of the solution to a very light shade ofbrown, and by the formation of a rather voluminous light-red colored,finely divided precipitate of the anacardate. The time required for thisreaction has varied from one hour and forty minutes to twenty-four hoursand it appears to depend to a considerable extent upon the amount ofwater present in the solution. The reaction is very slow in a drysolvent, but can be accelerated by heating the mixture over a waterbath,using a reflux condenser to minimize solvent loss.

At the completion of the above described reaction, the mixture wasfiltered by suction and the precipitate washed with fresh solvent. Theprecipitate was pressed and sucked as dry as possible after which it wasspread on paper to airdry. The yield of solvent-free salt wasapproximately 400 grams of calcium anacardate.

EXAMPLE 2 Regeneration of anacardic acid 400 grams of air-dried calciumsalt, prepared as described above in Example 1, were suspended withmechanical stirring in 3,000 cc. of hexane. A quantity of sulphuric acidcalculated to be more than equivalent to the calcium present in thesalt, as determined by ash analysis (in one instance, this equaled 90cc. H2304, sp. gr. 1.84), was diluted with eight parts of water. Thediluted sulphuric acid was added slowly but continuously from aseparatory funnel to the suspension of the calcium anacardate in hexane.The stirring was continued for one hour after the addition of the lastof the sulphuric acid. The precipitated calcium sulphate thus formed wascollected by filtration with a Buchner funnel. The filter cake was thenwashed several times with hexane, the washings being combined with thefirst filtrate. The hexane layer of the filtrate was separated in alarge separatory funnel and was washed several times with water untilthe wash water was neutral to litmus. Care was taken to shake thehexane-water mixture gently in order to avoid the formation of emulsionswhich are sometimes diflicult to break.

The washed hexane solution was heated to boiling in a fiask providedwith a vertical condenser and an automatic separator of theBidwell-Stirling type, whereby the water was removed from the system andthe hexane was returned to the flask. This operation was continued untilthe hexane solution of anacardic acid was free of water. The anacardicacid was recovered by distillation of the hexane under somewhat reduced-Preparation of calcium anacardate 10 grams of cashew nut shell liquid,containing 63.5% of anacardic acid, were dissolved in 640 cc. of 0.1normal sodium hydroxide solution, and clarified by filtration aftertreatment with 0.5 gram of charcoal and 2 grams of filtercel. The clearfiltrate was heated on a waterbath to a temperature of about C. andstirred mechanically. Tothis solution, 3.2 grams of calcium chloride(CaClz-ZHzO) in 58 cc. of water were added. Heating to maintain themixture at about 80 C. and stirring were continued for two and one-halfhours. Thereafter, the mixture was allowed to stand overnight. Theprecipitate thus formed was compacted by centrifuging and thesupernatant, turbid, aqueous layer was decanted. The precipitate wastransferred to a Buchner funnel, washed with 0.05 normal sodiumhydroxide solution by suction filtration, and finally airdried. Theyield was 7.3 grams of calcium anacardate. Anacardic acid can beregenerated from the calcium salt by the method described in Example 2above, or in Examples 5 and 6 following.

EXAMPLE 4 Preparation of calcium anacardate 32 grams of water were addedto 650 grams of cashew nut shell liquid containing about 55% ofanacardic acid and the resulting mixture was heated to 60 C. and mixedvigorously to uniformly disperse the water throughout the liquid. 111grams of slaked lime were added to this mixture and the mixing wascontinued for five minutes, during which time the temperature of themixture rose to C. Upon cooling to room temperature, the resultingsolidified plastic product was comminuted and leached with successiveportions of acetone until free from anacardol and other solubleconstituents of the cashew liquid. The acetone-wet calcium anacardatewas pressed and sucked as dry a possible, after which it was spread onpaper to air-dry.

It will be noted that the cashew liquid-water mixture was heated to 60C. This heatin was employed for the purpose of reducing the viscosity ofthe cashew liquid. It has been found that at temperatures below about 50C. the greater viscosity of the liquid inhibits the dispersion of thelime and the reaction between the anacardic acid and the lime thus tendsto be slow and cocasionally incomplete.

EXAMPLE 5 Regeneration of anacardic acid The ari-dried calcium salt,prepared as described above in Example 4, was treated with a solution of205 grams of oxalic acid in one litre of acetone. The mixture wasstirred for one hour while its temperature wa maintained at a point justbelow boiling. Following the stirring and heating, the solution wasfiltered to remove the precipitated calcium oxalate and the filteredprecipitate was washed with two portions of 200 cc. each of acetone. Thefiltrate and washings were combined and concentrated by distillation,the final traces of acetone being removed under reduced pressure. ,Thesmall amount of oxalic acid which crystallized from. the: anacardic acidupon cooling to room temperature-was removed by filtration. The yield ofanacardic acid was 317 grams, 71% of theory. Most probably, the majorportion of the loss was caused. by incomplete extraction of theanacardic acid from the precipitated calcium oxalate.

EXAMPLE 6 Regeneration of anacardic acid 1,000 grams of calciumanacardate, prepared as described in either Example 1, 3, or 4- above,weresuspended in 1500 cc. of hexane. Slowly and with vigorous stirring,742' cc, ofconcentrated' hydrochloric acid were added to thissuspension. The mixture became hot as the acid was added and gas wasevolved (CO2 from the CaCOz present). solid impurities, the mixturegradually dissolved to form a dark colored oil. The mixture was allowedto stand overnight whereupon it separated into two layers, namely, anupper layer of hexane and'an almost solid lower layer. The hexane layerwas decanted and a litre of hexane and a litre of water added to thelower layer. The mixture formed a gelatinous emulsion which was brokensomewhat by heating on a steam bath. After several hours standing, apart of the upper hexane layer could be decanted. The emulsion wasextracted twice more with one-litre portion of hexane and the decantedhexane combined with the two portions. of decanted hexane reviouslyobtained. The combined hexane extracts were concentrated slightly byevaporation and then refluxed to remove water, using the-Bid'well-Stirling type of separator, after which they were evaporated to recoverthe dissolved anacardic acid. The resulting anacardic acid was dark incolor, crystallized rapidly when cooled to below room temperature, andremained semi-solid at room temperature. The yield of anacardic acid was516 grams.

EXAMPLE 7 Hydrogenation of anacardic acid.

A one-litre flask was charged with 100 grams of' anacardic acid (M. P.C.), 500 cc; of 95% ethanol, and 0.5 gram of platinum oxide catalyst.The anacardic acid had been obtained as described in either Example 2,5, or'6 and subsequently purified by treatment with charcoal. The flaskwas shaken with hydrogen for" one hour; The heat of reaction warmedthe-mixture to about 40 C. The hydrogen absorbed amounted to 142 cc. C.)per gram oranacardic acid, i. e., 1.97 mols of hydrogen per mol of acid.

After hydrogenation was completed, the solution was filtered to removethe platinum oxide catalyst and treated. with 300" cc. of water, whichprecipitated the tetrahydroanacardic acid. After filtering and drying,this" material amounted to 9-7- grams, melted at about 9.0" C.,,and waslight brown in color. This. color was. removed by dissolving the productin one litre of water, at 70 C.80 0., containing sufficient' sodiumhydroxide The solution was to effect a final pH of 9-11. clarified byfiltration, and cooled to. about 0 C.. whereupon the sodiumtetrahydroanacardateprecipitated. The sodium salt was filtered. andwashed with a little cold water; One more recrystallization of thesodium. salt resulted in a pure white product, whichwas converted totetrahydroanacardic acid by pouring its solution into excess dilutehydrochloric acid. Theprecip tated:

With the exception of a small amount of 12' acid, after filtering anddrying amounted to 87 grams and melted at.90 C..-92 C.

EXAMPLE 8 Preparation of tetrahydroanacardic acid from cashew nut she'llliquid 600 grams of cashew nut shell liquid containing. 54.2% oranacardic acid were stirred for 0.5 hour with 23 grams of oxalic aciddissolved in 0.5 litre of acetone in order to precipitate any calciumion which may have. been present as an ash constituent in the liquid.The mixture was filtered and the acetone removed by distillation. Thecashew liquid was then washed with water to remove residual oxalic acid,the emulsions which formed in the later washings. being broken by theaddition of about 0.5 litre of hexane. The washing with water wascontinued until the water solution was neutral to litmus, after whichthe hexane was removed from the liquid by distillation. The purpose ofthe. above described acid treatment was to remove ash, such as CaO,etc.. from the cashew nut shell liquid, thus preventing possiblepoisoning of the hydrogenation catalyst and decarboxylationduringhydrogenation.

403.8. grams-of the cashew liquid treated as describedabove werehydrogenated for seven hours at 1,000 to 2,000 pounds per square inchpressure and at a temperature of 60 C. to C., using one teaspoonful ofRaney nickel asa hydrogenatingv catalyst. Titration of the hydrogenatedoil showed a tetrahydroanacardicacid content of 58.4 per cent.

250 grams of the hydrogenated cashew liquid were melted in a Monelmixing pot at amout 65 C'. and 125 cc. of water were added. 50 grams oflime were added to the mixture and stirred in thoroughly. The.temperature rose from 65 C. to C- The. product solidified after twohours standing.

The lime treated solid product was divided into five portions, each ofwhich was placed in a Soxhlet extractor and extracted with acetone forfive hours to remove the non-acidic portion of the liquid from thecalcium tetrahydroanacardate. Distillation of the acetone from theextract left a residue of the non-acidic portion of the liquid amountingto 88.5 grams (85 per cent. of theory). The calcium tetrahydroanacardatewas converted to the free acid by adding, a few hundred cc. at a time, asolution of 85 grams of oxalic acid in 2 litres of acetone. Afterstirring for about thirty minutes, the calcium oxalate was removed byfiltration an washed with acetone. The acetone washings were added tothe filtrate and the whole evaporated to dryness. The residue wasstirred with hot water to remove any remaining oxalic acid. Theresulting washed crude tetrahydroanacardic acid was, by titration, 87.4per cent. pure and amounted to 93.7 per cent. of theory, basedupon thetitres of the original cashew liquid and the final product. If desired,the acid could have been purified through the crystallization of itssodium salt as shown in Example '7.

EXAMPLE 9.

Purification of 'anacardic acid Crude anacardic, acid (88 %-90%) acidwas dissolved. in petroleum ether using 2.0 to 2.5 grams of acid per cc.of solvent. Thesolution was allowed to stand for a short time and thenfiltered to remove any insoluble material which might have been present.Darco KB- charcoal was added. to the filtered solution in an amountequal 13 to 30% to 50%, by weight, of the acid being treated. Themixture was shaken thoroughly and allowed to stand overnight, afterwhich the charcoal was filtered out. A fresh portion of charcoal wasadded, the mixture again allowed to stand overnight, and the charcoalfiltered out. The resulting solution of the acid was almost colorless.The petroleum ether was distilled from the acid, reduced pressure beinemployed to remove the last traces of solvent. The residual anacardicacid was light yellow in color and titrated greater than 98% acid.

EXAMPLE Recrystallization of anacardic acid at lozp temperatures Asolution of 100 grams of anacardic acid (90.2% pure) in 2 litres ofhexane was cooled from room temperature to 44 C. in one and one-halfhours. After maintaining this temperature for one and one-halfhoursmore, a solid began to separate from the solution. At the end of two andone-half hours at 40 C. the solution was filtered and the precipitatewas washed with 500 cc. of hexane at 43 C. This treatment yielded 52grams of 95.8% pure anacardic acid.

In a similar fashion, the filtrate and wash liquor were cooled to 60 C.and 35 grams of crystals of 89.5% purity were obtained. The remainingliquor contained 19 grams of anacardic acid of 79.6% purity.

EXAMPLE 11 Purification of anacardz'c acid Twenty grams of crudeanacardic acid, 923% acid, were dissolved in 100 cc. i-propanol and 100cc. of water containing sufiicient sodium hydroxide to raise the pH to9. This solution was extracted in a separatory funnel with four 100 cc.portions of benzene. The combined benzene extracts were washed with 50%i-propanol, then with a saturated solution of oxalic acid, and finallywith water. After drying, distillation of the benzene left 220 gramsdark oil which, by titration, was 1.14 grams anacardic acid and 1.06grams non-acidic material indicating, by difference, an acid yield of93.8% and an acid purity of 97.3%.

I claim:

1. The process for the separation of the acid constituent contained in aliquid. selected from the group consisting of cashew nut shell liquidand hydrogenated cashew nut shell liquid from toxic phenolic componentsof said liquid which comprises reacting alkaline earth metal ions withions of acid contained in said liquid to form a solid alkaline earthmetal salt of said acid and water of reaction, with which toxic phenoliccomponents of said liquid are associated, treating said mixture of solidsalt, water of reaction, and toxic phenolic components with awater-miscible solvent in which said toxic phenolic components aresoluble but in which said solid salt is sub stantially insoluble, toform a single liquid-phase comprising said toxic phenolic components,said water of reaction and said solvent, separating said liquid-phasefrom said solid salt, treating said separated salt with an acid capableof displacing the acid from said salt, and separating the liberated acidfrom the reaction mixture.

2. The process of claim 1 and wherein during the treatment of saidseparated salt with an acid capable of displacing the acid from saidsalt, the mixture of salt and acid is vigorousl agitated 14 and heatedto a temperature between about 50 C. and C. l.

3. The process of claim 2 and wherein the treatment of said separatedsalt with an acid capable of displacing the acid from said salt isconducted in the presence of a solvent for the liberated acid.

4. The process for the separation of the acid constituent contained in aliquid selected from the group consisting of cashew nut shell liquid andhydrogenated cashew nut shell liquid from toxic phenolic components ofsaid liquid which comprises reacting a basic alkaline earth metalcompound with acid contained in said liquid to form a solid alkalineearth metal salt of said acid and Water of reaction, with which toxicphenolic components of said liquid are associated, said reaction beingconducted in a water-miscible solvent in which said toxic phenoliccomponents are soluble but in which said solid salt is substantiallyinsoluble to form said solid alkaline earth metal salt as a finelydivided precipitate in a single liquid-phase comprising said toxicphenolic com ponents, said water of reaction and said solvent,separating said liquid-phase from said solid salt, treating saidseparated salt with an acid capable of displacing the acid from saidsalt, and separating the liberated acid from the reaction mixture.

5. The process of claim 4 wherein the alkaline earth metal compound isemployed in excess of that theoretically required to react with the acidto form the basic salt of the acid.

6. The process of claim 4 wherein the liquid treated is a cashew nutshell liquid containing at least 40% of anacardie acid; wherein thealkaline earth metal compound is slaked lime and is employed in excessof that theoretically required to react with the acid to form the basicsalt of the acid; and wherein the acid capable of displacing the acidfrom the alkaline earth metal salt is an acid which forms an insolublesalt with the alkaline earth metal.

7. The process for the separation of the acid constituent contained in aliquid selected from the group consisting of cashew nut shell liquid andhydrogenated cashew nut shell liquid containing at least 40% of saidacid from toxic phenolic components of said liquid which comprisesreacting a basic alkaline earth compound with acid contained in saidliquid, to form a hardened plastic mass comprising the alkaline earthmetal salt of said acid in solid form, water of reaction and said toxicphenolic components, the alkaline earth metal compound being used inexcess of that theoretically required to react with the acid to form aneutral salt, subdividing said hardened plastic mass, leaching saidsubdivided product with a water-miscible solvent in which said toxicphenolic components are soluble but in which said salt is substantiallyinsoluble, to form a single liquid-phase comprising said toxic phenoliccomponents, said water of reaction and said solvent and to separate saidtoxic phenolic components from said salt, treating such leached productwith an acid capable of displacing the acid from the alkaline earthmetal salt, and separating the liberated acid from the reaction mixture.

8. The process of claim 7 wherein the liquid treated is a cashew nutshell liquid containing at least 40% of anacardic acid; wherein thealkaline metal compound is slaked lime and is employed in excess of thattheoretically required to react with the acid to form a basic salt; and

wherein the acid capable of displacing the acid from the alkaline earthmetal salt is an acid which forms an insoluble salt with the alkalineearth metal.

9. The process for the separation of the acid constituent contained in aliquid selected from the group consisting of cashew nut shell liquid andhydrogenated cashew nut shell liquid from.

toxic phenolic components of said liquid which comprises converting acidcontained in said liquid into a water-soluble salt and reacting saidWatersoluble salt with a water-soluble alkaline earth metal salt to forma solid alkaline earth metal salt of said acid with which water ofreaction and toxic phenolic components of said liquid are associated,said reaction being conducted in a water-miscible solvent in which saidtoxic phenolic components are soluble but in which said solid salt issubstantially insoluble to form said solid alkaline earth metal salt asa finely divided precipitate in a single liquid-phase comprising saidtoxic phenolic components, said water of reaction and said solvent,separating said liquidphase from said solid salt, treating saidseparated salt with an acid capable of displacing the acid from saidsalt, and separating the liberated acid from the reaction mixture.

10. The process of claim 9 wherein the alkaline earth metal salt ispresent in excess of that theoretically required to form the basic salt.

11. The process of claim 9 wherein the liquid treated is a cashew nutshell liquid containing at least of anacardic acid; wherein thewatersoluble alkaline earth metal salt is a calcium salt and is presentin excess of that theoretically required'to form the basic salt of theacid; and wherein the acid capable of displacing the acid from thealkaline earth metal salt is an acid which forms an insoluble salt withthe alkaline earth metal.

ROLAND E. KREMERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,230,995 Balvalli Feb. 11, 19411,838,075 Harvey Dec. 22, 1931 2,000,244 Merrill May 7, 1935 2,170,506Reiber Aug. 22, 1939 2,132,356 Lecher Oct. 4, 1938 2,198,292 Reiff et alApr. 23, 1940 2,252,664 Reifi et al. Aug. 12, 1941

